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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_000_007_430">&nbsp;</a>NAME</h4><blockquote>
log1p - compute a natural logarithm
</blockquote><h4><a name = "tag_000_007_431">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="math.h.html">math.h</a>&gt;

double log1p (double <i>x</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_007_432">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>log1p()</i>
function computes log<sub><small>e</small></sub>(1.0 + <i>x</i>).  The value of
<i>x</i>
must be greater than -1.0.
</blockquote><h4><a name = "tag_000_007_433">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion,
<i>log1p()</i>
returns the natural logarithm of 1.0 +
<i>x.</i>
<p>
If <i>x</i> is NaN,
<i>log1p()</i>
returns NaN and may set <i>errno</i> to [EDOM].
<p>
If <i>x</i> is less than -1.0,
<i>log1p()</i>
returns -HUGE_VAL or NaN and sets <i>errno</i> to [EDOM].
<p>
If <i>x</i> is  -1.0,
<i>log1p()</i>
returns -HUGE_VAL and may set <i>errno</i> to [ERANGE].
</blockquote><h4><a name = "tag_000_007_434">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>log1p()</i>
function will fail if:
<dl compact>

<dt>[EDOM]<dd>
The value of <i>x</i> is less than -1.0.

</dl>
<p>
The
<i>log1p()</i>
function may fail and set <i>errno</i> to:
<dl compact>

<dt>[EDOM]<dd>
The value of <i>x</i> is NaN.

<dt>[ERANGE]<dd>
The value of <i>x</i> is -1.0.

</dl>
<p>
No other errors will occur.
</blockquote><h4><a name = "tag_000_007_435">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_436">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_437">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_438">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="log.html">log()</a></i>,
<i><a href="math.h.html">&lt;math.h&gt;</a></i>.
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]

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